The above data is usually obtained by means of the Marine Sextant or Theodolite with the help of almanacks and nautical tables.
The sextant is expensive and fragile and when teaching it is seldom feasible to provide each member of a class with his own instrument and set of reference volumes. The sextant requires a clear horizon. Consequently it cannot be used in most inland situations unless an artificial horizon is employed which is difficult to provide.
The required reference volumes are costly, bulky and require annual replacement. Use of the sextant and its attendant books demands of the student a relatively advanced knowledge of mathematics, and even when up-to-date tables are used there is much room for error and doubt. Furthermore very few students ever understand these tables, merely learning how to use them by rote.
An object of this invention therefore is to provide a robust and simple device for obtaining the above data which is at a price within reach of school budgets, which will provide the above information in an understandable manner and with sufficient accuracy to yield a navigational `fix` to the nearest whole degree of Longitude and Latitude in the absence of a sensible horizon; and which will yield a pilotage fix accurate enough for rough and ready coastal navigation when land marks are in sight.